Various repair methods can be employed to repair photolithography masks. Repair work can be affected, for example, using ion beams or what is called nano-machining. A repair based on irradiation of the material with laser beams can be well-suited for large defects. This method can be particularly well-suited for “opaque” defects, i.e., for defects wherein excessive material is present and needs to be removed. If the laser beam is supplemented by a depositing means for deposition of material, “transparent” defects can be corrected, i.e., defects where material is missing.
For defects having particularly small structures and for masks by which a high structural resolution is to be achieved, further methods can be better-suited, for example, a repair method based on electron beams. This method can enable removal of material in the case of “opaque” defects and the addition of material in the case of “transparent” defects. This is affected by an additional deposition mechanism, in which the electron beam induces a chemical reaction in the deposition material, so that the added molecules combine with the material structure. However, in the case of large defects, this method can be very slow, such that it can be efficiently employed only for small defects. On the other hand, the repair using laser beams enables the treatment of large defects. However, due to its low resolution, the method can be very inaccurate.
In known repair devices, only one of the methods is usually implemented. However, since both small and large defects may occur on one type of mask, the repair of the defects is complex and may take very long under certain circumstances. Also, such apparatus can be inflexible with respect to the repair of different types of mask—each type representing a structural resolution which is achievable by this mask on a wafer, e. g., 32 nm, 45 nm, 65 nm, or 90 nm.
WO 2004/006013A1 describes an arrangement for the production of photomasks that comprises a defect control system and one or more repair systems connected thereto, all systems being connected to each other via data links, thus enabling a mutual influence. Both material-depositing and material-removing devices can be used as repair systems. For example, the arrangement may comprise a laser removal system, an atomic force microscope, an ion beam system or an electron beam-based depositing system. The arrangement described in WO 2004/006013A1 may comprise a database system which can make a repair suggestion for detected defects that are known and have been previously stored. An essential aspect of WO 2004/006013A1 is the integration of measurement and repair systems within the arrangement for producing the mask. In this case, a defect is analyzed in the arrangement and one of several repair methods is selected. This step can be carried out repeatedly. However, this arrangement is designed for the repair of only one type of mask.
There is therefore a need for an improved method and device for the repair of photolithography masks.